1. Field of the Invention
This invention relates to handling hand and hoist line implements; and more particularly to a grapple for use in oil well drilling.
2. Description of the Prior Art.
Often in drilling oil wells, gas under pressure is present at the bottom of the well. This gas pressure sometimes tends to cause a blowout. To prevent this, a rotating head is placed at the top of the well. The rotating head forms a seal between the stationary, permanent casing at the top of the well and the rotating drill pipe, which carries the bit on the bottom. The rotating head permits the drill pipe string to run down through it and maintain a seal to it. The seal to the rotating drill pipe rotates with the drill pipe, and the portion attached to the casing remains stationary. A typical rotating head weighs about 200 kg or more. Each time the drill string is pulled from the well, it is necessary to pull the rotating head from the casing and set it to one side on the drill rig floor. It is highly desirable not to permit the drill pipe to come out of the rotating head because it is difficult to insert the pipe through the rotating head again.
Therefore, according to common practice before this invention, a "cat" line or a short line is attached to the drilling head to hold it on fixed relationship to a section of drill pipe as it is pulled out of the well. Then, this section or stand of the drill pipe with the rotating head and cat line on it is set over to one side of the drilling rig floor. As soon as it is on the floor, some sort of device is attached to the drill pipe immediately below the rotating head. Prior to my invention, this device was in the form of pipe tongs, which were attached to the drill pipe immediately below the rotating head or, sometimes, a heavy rope was taken and wrapped around the drill pipe three or four times so it would form a friction hold on the drill pipe and, thus, maintaining the rotating head above the device.
The disadvantages of the prior art that if drill tongs are used, they project from the drill pipe, forming an obstruction on the drill rig floor. Also, obviously, often the pipe tongs are needed for some other function and are not available. If a rope is wrapped around a drill pipe, often the rope comes loose, sometimes causing a loss of fingers of the workmen. Also, those skilled in the art will understand that the drill pipe is greasy and covered with mud, making the equipment extremely difficult to handle.